OBJECTIVES: To assess the impact of modifiable risk factors on obesity among high school students in the U.S. and to estimate the population attributable risks (PAR) of modifiable risk factors.

METHODS: This study employed a retrospective analysis of the 2015 Youth Risk Behavior Surveillance System (YRBSS) data. Obesity was defined as ≥95th percentile for body mass BMI, based on sex- and age-specific data from CDC. Unhealthy dietary behaviors, physical inactivity, and other modifiable risk factors – lack of physical education, amount of sleep (eight or less hours of sleep), smoking, time spent on computers (three or more hours per day), and time spent watching TV (three or more hours per day) were included in analysis. Multivariable logistic regression was performed to assess the association between unhealthy dietary behaviors, physical inactivity, and other modifiable risk factors and obesity and to calculate PARs, controlling for the respondent’s age, gender, and race. The complex survey design used in YRBSS was taken into account in all analyses. Standard errors and 95% confidence limits of PARs were estimated using the Jackknife repeated replication (JRR) method.

RESULTS: A total of 15,624 individuals, with nearly 13% being classified as obese, were included in study. Not being on a sports team (OR:1.534; 95% CI:1.235-1.905), currently smoking (OR:1.288; 95% CI:1.060-1.565), and over 3 hours/day of TV (OR:1.382; 95% CI:1.093-1.747) were found to be significant risk factors of obesity. PAR for not being on a sports team was 15.34% (95% CI: 14.58-16.11%), over 3 hours/day of TV was 7.37% (95% CI: 6.48-8.26%), and currently smoking was 3.69% (95% CI: 3.24-4.15%). The overall PAR for all significant risk factors combined was 24.72% (95% CI: 24.45-24.98%).

CONCLUSIONS: Findings about PAR help demonstrate the relative importance of physical activities, smoking behavior, and sedentary lifestyles among adolescents with regard to obesity.